Controls for multi-compressor refrigeration systems



March 15, 1966 w, K, KYLE 3,240,027

CONTROLS FOR MULTI-COMPRESSOR REFRIGERATION SYSTEMS Filed July 1, 1964 BY A THERMosTAT wy M* SWITCHES United States Patent 3,240,027 CONTROLS FOR MULTI-COMPRESSOR REFRIGERATION SYSTEMS William K. Kyle, 120 Sproul Lane, Staunton, Va. Filed July 1, 1964, Ser. No. 379,584 12 Claims. (Cl. 62-126) This invention relates to refrigeration systems using two or more refrigerant compressors, and has as an object to improve the safety circuits of such compressors.

In an air conditioning system using, for example, two refrigerant compressors, when the load requires that both compressors operate, a safety control of one of the compressors may shut down the system, stopping both compressors. Since the compressors are usually hidden from View, there is no readily available means for indicating to a responsible person which compressor is in trouble. One approach to the problem has been to provide switches that can be operated to disconnect one compressor and to restart the other. The operator has had to guess, however, which compressor is in trouble. The good compressor may be disconnected, and the troubled compressor restarted. Under some conditions, a troubled compressor can be restarted and operated for several minutes before again tripping off.

This invention provides a solution to this problem by providing controls which, when one compressor is in trouble, 'stop both compressors, and light a lamp on a control panel adjacent to a control switch of the troubled compressor, clearly indicating which compressor is in trouble. A responsible person then operates the control switch which restarts the good compressor. The control switch is mechanically connected to another switch which automatically disconnects the troubled compressor. Thus, the system can operate on one compressor while steps are taken to have the troubled compressor repaired.

This invention will now be described with reference to the annexed drawings, of which:

FIG. 1 is a diagrammatic view of an air conditioning system embodying this invention;

FIGS. 2a and 2b are diagrammatic views of the overload relays used;

FIGS. 2c and 2d are diagrammatic views of the cooling control relays used;

FlGS. 2e and 2f are diagrammatic views of the compressor motor starter used;

FIGS. 2g and 2h are diagrammatic views of the protective relays used, and

FIG. 3 is a simplified, electrical control circuit of the system.

Referring first to FIG. l, evaporator coils EI and E2 are stacked in a vertical row in a casing or duct 10. A fan EF1 driven by an electric motor EFMI, moves air to be cooled `over the surface of the coil EI. A fan BF2 driven by an electric motor EFMZ, moves air to be cooled over the surface of the coil E2. The coil E1 is connected by lsuction line II to the suction side of hermetic compressor C1, the flow being through motor CMI of the compressor C1 as is usual in hermetic compressors. The discharge side of the compressor C1 is connected through high pressure cut-out HPCI, condenser coil 20, and expansion valve V1 to the coil E1.

The cut-out HPCI has a normally closed switch HPCIS. A thermostat MT1 exposed to heat from the motor CM1, has a normally closed switch MTlS. A fan CF1 driven by an electric motor CFMI moves outdoor air over the surface of the condenser coil 20.

The evaporator lcoil E2 is connected by suction line 14 to the suction side of a hermetic compressor C2 driven by an electric motor CM2. The discharge side of the compressor C2 is connected through high pressure cut-out ice HPCZ, condenser coil 21, and expansion valve V2 to the coil E2.

The cut-out HPC2 has a normally closed switch HPCZS. A thermostat MT2 exposed to heat from the motor CM2, has a normally closed switch MT2S. A fan CP2 driven by an electric motor CFMZ moves outdoor air over the surface of the condenser coil 21.

Referring now to FIG. 3, an indoor, iirst-stage, cooling control thermostat switch 1TS1 is connected in series with cooling relay CRI to secondary winding 16 of stepdown transformer lI7, primary winding 18 of which is connected to electric supply lines LI and L2. The compressor motor CM1 is connected in series with switch MSIS of motor starter MSI and overload relay OLRI to the supply lines. The starter MSI is connected in series with protective relay PR2, normally closed switch BPSISZ, normally open switch CRIS of the cooling relay CR1, which is connected in parallel with normally open switch PRISZ of the protective relay PR1, and protective relay PR2 to the supply lines. Normally closed switches PRISI of the relay PR1, OLRIS of the overload relay OLRI, HPCIS of the cut-out HPCI, and MTIS of the motor thermostat MT1 are connected in series across the relay PRI, normally forming a short-circuit across the latter. Normally closed switches PRZSI of the protective relay PR2, OLRZS of overload relay OLRZ, HPCZS of the cut-out HPCZ, and MT2S of the motor thermostat MT2 are connected in series across the relay PR2, normally forming a short-circuit across the latter.

High impedance lamps B1 and B2, such as neon lamps, are connected across the relays PRI and PR2 respectively. A normally open, by-pass switch BPSISI is connected across the relay PR1, the lamp B1 :being located adjacent to this switch. A normally open, by-pass switch BPSZSI is connected across the relay PR2, the lamp B2 being located adjacent to this switch. The compressor motor CM2 is connected in series with the switch MSZS of motor starter MS2 and the overload relay OLRZ to the supply lines.

An indoor, second-stage, cooling control thermostat ITSZ is connected in series with cooling relay CRZ to the secondary winding 16 of the transformer 17. The motor starter MS2 is connected in series with the protective relay PR1, shunted by the closed switches PRISI, OLRIS, HPClS and MTIS, normally closed switch BPS2S2, normally open switch CR2S of the cooling relay CR2, which is connected in parallel with normally open switch PR2S2 of the relay PR2, and the relay PR2, shunted by the closed switches PRZSI, OLRZS, HPCZS and MTZS, to the supply lines.

The switches BPSISI and BPSISZ are connected by pivoted linkage 24- so that when the switch BPSISI is manually closed, the switch BPSISZ is automatically opened, and vice versa. The switches BPSZSI and BPS2S2 are connected by pivoted linkage 25 so that when the switch BPS2S1 is manually closed, the switch BPS2S2 is automatically opened, and vice versa.

The protective relays PRI and PR2 have relatively large impedances, and the motor starters M81 and MS2 have relatively small impedances. The starters MSI and MS2 are each connected in series with both protective relays PRI and PR2, and when either of the latter is energized by the opening of one of the switches connected in series across it, both motor starters MSI and MS2 are deenergized. This form of protective relay is disclosed in the US. patent of A. W. Courtney, Jr., No. 2,697,195.

NORMAL OPERATION In operation, when the first stage, thermostat switch ITSI closes, it energizes the cooling relay CRI which closes its switch CRIS. The latter connects the motor starter MSI through the relay PR1 shunted by the closed 3 switches MTIS, HPCIS, OLRIS and PRISI, the closed switch BPSISZ, the relay PRZ shunted by the closed switches PRZSI, OLR2S, HPCZS and MT 2S to the supply lines LI and L2. The starter MSI is energized and closes its switch MSIS, starting the compressor motor CMI.

When the second stage, thermostat switch ITSZ closes, it energizes the cooling relay CRZ which closes its switch CRZS. The latter connects the motor starter MS2 through the relay PR2 shunted by the closed switches MTZS, HPCZS, OLR2S and PRZSI, the closed switch BPS2S2, and the relay PRI shunted by the closed switches PRISi, OLRIS, HPCIS and MTIS to the supply lines. The starter MS2 is energized and closes its switch MSZS, starting the compressor motor CM2.

When the compressor CI is started by the energization of its motor CMI, it supplies refrigerant through the condenser coil 20 and expansion valve VI to the evaporator coil E1, the refrigerant expanded in the latter cooling the air passed by the fan EF1 over its surface. When the compressor C2 is started by the energization of its motor CM2, it supplies refrigerant through the condenser coil 2li and expansion valve V2 to the evaporator coil E2, the refrigerant expanded in the latter cooling the air passed by the fan EF2 over its surface.

The energizing circuits for the indoor fan motors EFMI and EFMZ, and the outdoor fan motors CFMI and CFM2 are not shown since their operation is conventional.

Compressor C1 in trouble If abnormally high refrigerant pressure causes the protective switch HPCIS to open, or excessive motor current causes the switch OLRIS to fopen, or excessive motor temperature causes the switch MTIS to open, the short-circuit across the protective relay PRI is opened, and the relay PRI is energized. The voltage drop across the relay PRI causes the lamp B1 to light indicating that the compressor CI is in trouble. The relay PRI is now connected in series with both motor starters MSI and MS2, and its irnpedance is so large that it deenergizes the motor starters, stopping both compressors CI and C2. The relay PRI opens its switch PRISI and closes its switch PRISZ. The closed switch PRIS2 connected across the cooling relay switch CRIS prevents the possible opening `of the latter by the opening of the thermostat switch ITSI from deenergizing the relay PRI. The now open switch PRISI prevents the deenergization of the relay PRI, when the fault was temporary, and the protective switch which opened the short-circuit across the relay PRI reclosed. Since such temporary trouble is likely to recur, the relay PRI should remain energized.

The responsible person on noting that the light BI is on, should close the switch BPSISI which opens the switch BPSISZ.. The opening of the latter switch disconnects the starter MSI, stopping the compressor CI. The now closed switch BPSSI is shunted across the relay PRI, removing its impedance from in series with the motor starter MS2, reenergizing the latter which closes its switch MSZS, restarting the good compressor C2.

Compressor C2 in trouble lf abnormally high refrigerant pressure causes the protective switch HPCZS to open, or excessive motor current causes the switch OLRZS to open, or excessive motor temperature causes the switch MTZS to Open, the short-circuit across the protective relay PR2 is opened, and the relay PR?. is energized. The voltage drop across the relay PR2 causes the lamp B2 to light, indicating that the compressor C2 is in trouble. The relay PR2 is now connected in series with both motor starters MSI and MS2, and its impedance is so large that it deenergizes the motor starters, stopping both compressors CI and C2. The relay PRZ opens its switch PRZSI and closes its switch PRZSZ. The closed switch PRZSZ connected across the cooling relay switch CRZS prevents the possible opening of the latter by the opening of the thermostat switch 1TS2 from deenergizing the relay PR2. The now open switch PRZSI prevents the deenergization of the relay PRZ when the fault was teniporary, and the protective switch which opened the shortcircuit across the relay PR2 reclosed.

The responsibe person on noting that the light B2 is on, Should close the switch BPSZSI which opens the switch BPS2S2. The opening of the latter switch disconnects the motor starter MS2, stopping the compressor C2. The now closed switch BPSZSI is shunted across the relay PR2, removing its impedance from in series with the motor starter MSI, reenergizing the latter which recloses its switch MSIS, restarting the good compressor C1.

This invention permits an unskilled person to easily and quickly determine which compressor of a multi-compressor system is in trouble when the system is shut down because of compressor trouble, and to restart the good compressor, or compressors when more than two compressors are used, while arranging for servicing of the troubled compressor.

What is claimed is:

1. A refrigeration system comprising a compressor, a irst electric motor for driving said compressor, a condenser coil and an evaporator coil connected with said compressor in a refrigeration circuit, a second compressor, a second electric motor for driving said second compressor, a second condenser coil and a second evaporator coil connected with said second compressor in a second refrigeration circuit, a starter for said first motor, said starter having a winding and having a switch that is closed when said winding is energized, a second starter for said second motor, said second starter having a second winding and having a second switch that is closed when said second Winding is energized, A.C. supply connections, means connecting said switch of said rst mentioned starter and said first motor in series to said connections, means connecting said second switch and said second motor in series to said connections, a first protective relay having a winding and having a normally closed switch that opens when said last mentioned winding is energized, a second protective relay having a winding and having a normally closed switch that opens when said last mentioned winding is energized, said windings of said relays having impedances substantially larger than the impedances of said windings of said starters, a irst safety control for said lirst compressor, said control having a normally closed switch that opens when said first compressor is in trouble, means including said switches of said first relay and of said control in series forming a short-circuit across said winding of said rst relay, a second safety control for said second compressor, said second control having a normally closed switch that opens when said second compressor is in trouble, means including said switches of said second relay and of said second control in series forming a short-circuit across said winding of said second relay, means connecting said windings of said relays and of said iirst mentioned starter in series to said connections, and means connecting said windings of said relays and of said second starter in series to said connections.

2. A refrigeration system as claimed in claim 1 in which high impedance signal lamps are connected across said windings of said relays.

3. A refrigeration system as claimed in claim I in which a normally open switch is connected across said winding of said iirst relay, in which a normally closed switch is included in said means connecting said windings of said relays and of said first mentioned starter to said connections, in which said last mentioned switches are mechanically connected so that when said last mentioned open switch is closed, said last mentioned closed switch is opened, in which a normally open switch is connected across said winding of said second relay, in which a normally closed switch is included in said means connecting said windings of said relays and of said second starter to said connections, and in which said last mentioned switches are mechanically connected so that when said last mentioned open switch is closed, said last mentioned closed switch is opened.

4. A refrigeration system as claimed in claim 3 in which high impedance signal lamps are connected across said windings of said relays.

5. A refrigeration system comprising a compressor, an electric motor for driving said compressor, a condenser coil and an evaporator coil connected with 4said compressor in a refrigeration circuit, a second compressor, a second electric motor for driving said second compressor, a second condenser coil and a second evaporator coil connected with said second compressor in a second refrigeration circuit, a starter for said first mentioned motor, said starter having a first winding and having a first switch that is closed when said winding is energized, a second starter for said second motor, said second starter having a second winding and having a second switch that is closed when said second winding is energized, electric supply connections, means connecting said first mentioned switch and said first motor in series to said connections, means connecting said second switch and said second motor in series to said connections, a first protective relay having a winding and having a normally open switch that closes when said last mentioned winding is energized, a second protective relay having a winding and having a normally open switch that closes when said last mentioned winding is energized, said windings of said relays having impedances substantially larger than the impedances of said windings of said starters, a first safety control for said first compressor, said control having a normally closed switch that opens when said first compressor is in trouble, means including said switch of said control forming a short-circuit across said winding of said first relay, a second safety control for said second compressor, said second control having a normally closed switch that opens when said second compressor is in trouble, means including said switch of said second control forming a shortcircuit across said winding of said second relay, a first cooling relay having a normally open switch that closes when said cooling relay is energized, a first-stage thermostat switch, means connecting said thermostat switch and said cooling relay in series to said connections, means including said switch of said cooling relay connecting said windings of said first and second relays and of said first mentioned starter in series to said connections, said switch of said first relay being connected across said switch of said cooling relay, a second cooling relay having a normally open switch that closes when said second cooling relay is energized, a second-stage thermostat switch, means connecting said second-stage switch and said second cooling relay in series to said connections, means including said switch of said second cooling relay connecting said windings of said first and second relays and of said second starter in series to said connections, said switch of said second relay being connected across said switch of said second cooling relay.

6. A refrigeration system as claimed in claim 5 in which high impedance signal lamps are connected across said windings of said first and second relays.

7. A refrigeration system as claimed in claim 5 in which a normally open switch is connected across said Winding of said first relay, in which a normally closed switch is included in said means connecting said windings of said first mentioned and second relays and of said first starter to said connections, in which said last mentioned switches are mechanically connected so that when said last mentioned open switch is closed, said last mentioned closed switch is opened, irl which a normally open switch is connected across said winding of said second relay, in which said means connecting said windings of said first and second relays and of said second starter to said connections includes a normally closed switch, and in which said last mentioned switches are mechanically connected so that when said last mentioned open switch is closed, said last mentioned closed switch is opened.

8. A refrigeration system as claimed in claim 7 in which high impedance signal lamps are connected across said windings of said first and second relays.

9. A refrigeration system as claimed in claim 5 in which said first relay has a normally closed switch connected in series with said switch of said first control across said winding of said first relay, and in which said second relay has a normally closed switch connected in series with said switch of said second control across said winding of said second relay.

10. A refrigeration system as claimed in claim 9 in which high impedance signal lamps are connected across said windings of said first and second relays.

11. A refrigeration system as claimed in claim S in which a normally open switch is connected across said winding of said first relay, in which a normally closed switch is included in said means connecting said windings of said first mentioned and second relays and of said first starter to said connections, in which said last mentioned switches are mechanically connected so that when said last mentioned open switch is closed, said last mentioned closed switch is opened, in which a normally open switch is connected across said winding of said second relay, in which a normally closed switch is included in said means connecting said windings of said first and second relays and of said second starter to said connections, in which said last mentioned switches are mechanically connected so that when said last mentioned open switch is closed, said last mentioned closed switch is opened, in which said first relay has a normally closed switch connected in series with said switch of said first control across said winding of said first relay, and in which said second relay has a normally closed switch connected in series with said switch of said second control across said winding of said second relay.

12. A refrigeration system as claimed in claim 11 in which high impedance signal lamps are connected across said windings of said first and second relays.

References Cited by the Examiner UNITED STATES PATENTS 3,059,448 l0/1962 McGrath 62--510 X 3,103,794 8/1963 Kyle et al 62-510 X 3,105,362 10/1963 Gould 62-126 ROBERT A. OLEARY, Primary Examiner. 

1. A REFRIGERATION SYSTEM COMPRISING A COMPRESSOR, A FIRST ELECTRIC MOTOR FOR DRIVING SAID COMPRESSOR, A CONDENSER COIL AND AN EVAPORATOR COIL CONNECTED WITH SAID COMPRESSOR IN A REFRIGERATION CIRCUIT, A SECOND COMPRESSOR, A SECOND ELECTRIC MOTOR FOR DRIVING SAID SECOND COMPRESSOR, A SECOND CONDENSER COIL AND A SECOND EVAPORATOR COIL CONNECTED WITH SAID SECOND COMPRESSOR IN A SECOND REFRIGERATION CIRCUIT, A STARTER FOR SAID FIRST MOTOR, SAID STARTER HAVING A WINDING AND HAVING A SWITCH THAT IS CLOSED WHEN SAID WINDING IS ENERGIZED, A SECOND STARTER FOR SAID SCOND MOTOR, SAID SECOND STARTER HAVING A SECOND WINDING AND HAVING A SECOND SWITCH THAT IS CLOSED WHEN SAID SECOND WINDING IS ENERGIZED, A.C.SUPPLY CONNECTIONS, MEANS CONNECTING SAID SWITCH OF SAID FIRST MEMTIONED STARTER AND SAID FIRST MOTOR IN SERIES TO SAID CONNECTIONS, MEANS CONNECTING SAID SECOND SWITCH AND SAID SECOND MOTOR IN SERIES TO SAID CONNECTIONS, A FIRST PROTECTIVE RELAY HAVING A WINDING AND HAVING A NORMALLY CLOSED SWITCH THAT OPENS WHEN SAID LAST MENTIONED WINDING IS ENERGIZED, A SECOND PROTECTIVE RELAY HAVING A WINDING AND HAVING A NORMALLY CLOSED SWITCH THAT OPENS WHEN SAID LAST MENTIONED WINDING IS ENERGIZED, SAID WINDINGS OF SAID RELAYS HAVING IMPEDANCES SUBSTANTIALLY LARGER THAN THE IMPEDANCES OF SAID WINDINGS OF SAID STARTERS, A FIRST SAFETY CONTROL FOR SAID FIRST COMPRESSOR, SAID CONTROL HAVING A NORMALLY CLOSED SWITCH THAT OPENS WHEN SAID FIRST COMPRESSOR IS IN TROUBLE, MEANS INCLUDING SAID SWITCHES OF SAID FIRST RELAY AND OF SAID CONTROL IN SERIES FORMING A SHORT-CIRCUIT ACROSS SAID WINDING OF SAID FIRST RELAY, A SECOND SAFETY CONTROL FOR SAID SECOND COMPRESSOR, SAID SECOND CONTROL HAVING A NORMALLY CLOSED SWITCH THAT OPENS WHEN SAID SECOND COMPRESSOR IS IN TROUBLE, MEANS INCLUDING SAID SWITCHES OF SAID SECOND RELAY AND OF SAID SECOND CONTROL IN SERIES FORMING A SHORT-CIRCUIT ACROSS SAID WINDING OF SAID SECOND RELAY, MEANS CONNECTING SAID WINDINGS OF SAID RELAYS AND OF SAID FIRST MENTIONED STARTER IN SERIES TO SAID CONNECTIONS, AND MEANS CONNECTING SAID WINDINGS OF SAID RELAYS AND OF SAID SECOND STARTER IN SERIES TO SAID CONNECTIONS. 